JP2001075053A - Display device of rear surface projecting type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve luminance and picture by making the polarizing direction of at least a green component among video light to be irradiated on a screen to be parallel with the vertical cross section of the screen so as to improve the using efficiency of the video light to be projected. SOLUTION: Video light emitted from a projection unit 2 is successively reflected by mirrors 3 to 5 and then, irradiated to a mirror 6 arranged on the rear surface of a casing 1. The video light irradiated on a plane mirror 6 is irradiated on the rear surface of a screen 7 arranged on the front surface opening part of the easing 1 obliquely from a lower side to form an image. Then, since the polarizing direction of at least a green component among video light to be irradiated on a screen 7 is made to be parallel with the vertical cross section of the screen 7, reflection on the screen 7 can be reduced to improve luminance. In addition to this, double images generated by projection of reflected light on the screen 7 can be suppressed to improve picture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection display device for obliquely projecting image light on the rear surface of a screen and observing an image from the front of the screen.

[0002]

2. Description of the Related Art An example of a conventional rear projection display device is shown in FIG.
And FIG. FIG. 9 is a cross-sectional view illustrating a schematic configuration of a conventional rear projection display device, and FIG. 10 is a top view illustrating a schematic configuration of a projection unit in the rear projection display device of FIG. In the following description, a coordinate system in which the width direction of the rectangular screen 170 is the x axis, the height direction of the screen 170 is the y axis, and the direction perpendicular to the screen 170 is the z axis will be described.

In this rear projection display device, a projection unit 120 is disposed in a housing 110 as shown in FIG. A projection lens 130 is arranged at a light exit of the projection unit 120. A reflection mirror 160 is arranged on the back surface inside the housing 110, and a transmissive diffusion screen 170 is arranged on the front surface of the housing 110. Then, the image light that is enlarged and projected from the projection unit 120 via the projection lens 130 is reflected by the reflection mirror 160, and then is irradiated from the back side of the diffusion screen 170, and the image is projected from the front side of the diffusion screen 170. To be observed.

As shown in FIG. 10, the projection unit 120 includes a white light source 121 composed of a lamp 121a and a reflector 121b, and white light emitted from the white light source 121 is used as dichroic mirrors 122 and 123.
Is separated into three colors. The first dichroic mirror 122 selectively reflects red component light (hereinafter, referred to as red light) of the white light emitted from the lamp 121a, and transmits other color component light. The second dichroic mirror 123 selectively reflects green component light (hereinafter, referred to as green light). Of the light transmitted through the first dichroic mirror 122, green light is selectively reflected by the second dichroic mirror 123 and guided to the green liquid crystal panel 127g. The remaining blue component light transmitted through the second dichroic mirror 123
Blue light) is reflected by the second and third reflection mirrors 12.
5, 126 are guided to the liquid crystal panel 127b for blue. The red light reflected by the first dichroic mirror 122 is guided to the liquid crystal panel 127r for red by the first reflecting mirror 124.

[0005] Each liquid crystal panel 127r, 127g, 127
b is modulated by the dichroic prism 1
The light is combined at 28 and emitted to the projection lens 130.

At this time, each of the liquid crystal panels 127r, 127
The incident direction of each color light modulated by g and 127b on the dichroic prism 128 is set in consideration of the color reproducibility of the dichroic prism 128. That is, the light reflected by the dichroic prism 128 is S-polarized light, and the transmitted light is P-polarized light.

Here, the S-polarized light refers to linearly polarized light in which the vibration direction of the electric vector of the light incident on the sample surface is perpendicular to the plane including the normal to the sample surface and the normal to the wavefront which is the traveling direction of the light. .
The P-polarized light refers to linearly polarized light in which the vibration direction of the electric vector of light incident on the sample surface is included in the incident surface (a plane including the normal to the sample surface and the traveling direction of the light).

Specifically, the dichroic prism 12
The red light of the light incident on 8 is set to S-polarized light with respect to the bonding surface 128x. That is, a component having a polarization direction perpendicular to the xz plane is reflected by the bonding surface 128x.
The green light is set to P-polarized light with respect to the bonding surfaces 128x and 128y. That is, a component having a polarization direction parallel to the xz plane is transmitted through the bonding surfaces 128x and 128y. Further, the blue light is set to S-polarized light with respect to the bonding surface 128y. That is, a component having a polarization direction perpendicular to the xz plane is reflected by the bonding surface 128y. Thus, the red light, the green light, and the blue light are color-combined.

[0009] The color-combined image light is transmitted from the projection lens 130 to the screen 17 via the reflection mirror 160.
0 is irradiated on the back side.

In recent years, a device for irradiating the screen 170 with image light obliquely has been proposed in order to reduce the thickness of the rear projection display device having such a configuration.
When the above-described projection unit 120 is used for such oblique projection, the screen 17 of the projected image light is used.
The polarization direction with respect to 0 is the dichroic prism 128
Is orthogonal to the polarization direction. That is,
The red component is P-polarized light, the green component is S-polarized light, and the blue component is P-polarized light.

By irradiating the screen 170 with image light obliquely, light is incident from the air onto the acrylic resin at a certain incident angle from normal incidence. FIG. 6 is a graph showing the reflectance characteristics of light incident on the acrylic resin from the air. As shown in FIG.
When the image light is irradiated obliquely to the screen 170, the component light that becomes P-polarized light with respect to the screen 170 reduces the reflectance at the screen 170, while the component light that becomes S-polarized with respect to the screen 170. Light tends to increase the reflectance at the screen 170.

The graph shown in FIG. 8 shows the relative luminous efficiency characteristics of a person. As shown in FIG. 8, the relative luminous efficiency of the human eye is highest near the wavelength of 555 nm corresponding to green, and tends to feel green light brighter than red light and blue light.

For this reason, when oblique projection is performed using the conventional projection unit 120, the reflectance of the brightest green light on the screen 170 increases, and not only does the overall brightness decrease, but also the reflected light is reflected. There is a problem that the image quality is reduced due to the inset.

[0014]

By irradiating the screen 170 with image light obliquely, light is incident from the air onto the acrylic resin at a certain incident angle from the perpendicular incidence. FIG. 6 is a graph showing the reflectance characteristics of light incident on the acrylic resin from the air.
As shown in FIG. 6, when the screen 170 is irradiated with image light obliquely, the light of the component that becomes P-polarized light with respect to the screen 170 is reflected on the screen 170 while the reflectance of the screen 170 decreases. On the other hand, the light of the component that becomes S-polarized light tends to increase the reflectance on the screen 170.

The graph shown in FIG. 8 shows the relative luminous efficiency characteristics of a person. As shown in FIG. 8, the relative luminous efficiency of the human eye is highest near the wavelength of 555 nm corresponding to green, and tends to feel green light brighter than red light and blue light.

For this reason, when oblique projection is performed using the conventional projection unit 120, the reflectance of the brightest green light on the screen 170 increases, so that not only does the overall luminance decrease, but also the reflected light is reflected. There is a problem that the image quality is reduced due to the inset.

The present invention has been made in view of such a problem, and it is possible to improve the luminance and the image quality by improving the utilization efficiency of image light projected obliquely to a screen. It is an object to provide a rear projection display device.

[0018]

SUMMARY OF THE INVENTION The present invention provides a light source lamp, color separation means for separating light emitted from the light source lamp into a plurality of color components, and an optical system for each color light separated by the separation means. A plurality of liquid crystal panels for modulation, a color synthesizing means for synthesizing each color light modulated by the liquid crystal panels, and an image light color-synthesized by the color synthesizing means projected onto the screen from obliquely above or below. Rear projection display device, comprising: a projection unit that emits light to the screen, wherein a polarization direction of at least a green component of image light applied to the screen is parallel to a vertical cross section of the screen. .

When projecting image light obliquely from above or below the screen, the angle between the principal ray of light incident on the screen and the normal to the screen is greater in the vertical direction than in the horizontal direction. growing. For this reason, by making the polarization direction of the green component of the image light having high relative luminous efficiency to the human eye parallel to the vertical cross section of the screen, the amount of light that is lost by reflecting the image light to the back surface of the screen is reduced. .

More specifically, a polarization direction adjusting means for adjusting the polarization direction of at least the green component of the image light synthesized by the color synthesizing means to be parallel to the vertical section of the screen is provided. It is characterized by.

With this configuration, when the green component of the image light synthesized by the color synthesizing unit is not parallel to the vertical cross section of the screen, the polarization direction adjusting unit controls the vertical cross section of the screen. Is adjusted to be parallel to

Preferably, the polarization directions of all the color components of the image light applied to the screen are parallel to the vertical section of the screen.

More specifically, the color components in the polarization direction orthogonal to the vertical section of the screen in the image light combined by the color combining means are adjusted to be selectively parallel to the vertical section of the screen. It is characterized by comprising a polarization direction adjusting means.

With such a configuration, of the image light synthesized by the color synthesizing means, the color component in the polarization direction orthogonal to the vertical section of the screen is selectively made parallel to the vertical section of the screen. It is adjusted to become.

Further, the present invention provides a light source lamp, a color separation means for separating light emitted from the light source lamp into a plurality of color components, and a plurality of optical modulators for optically modulating each color light separated by the separation means. A liquid crystal panel, a color synthesizing means for synthesizing each color light modulated by the liquid crystal panel, and a projection means for projecting the image light color-synthesized by the color synthesizing means from an oblique side to a screen. Wherein the polarization direction of at least the green component of the image light applied to the screen is parallel to the horizontal cross section of the screen.

When projecting image light from an oblique side to the screen, the angle between the principal ray of light incident on the screen and the normal to the screen is greater in the horizontal direction than in the vertical direction. . For this reason, by making the polarization direction of the green component of the image light having high relative luminous efficiency to the human eye parallel to the horizontal section of the screen, the amount of light that is lost by reflecting the image light on the back surface of the screen is reduced. .

More specifically, a polarization direction adjusting means for adjusting the polarization direction of at least the green component of the image light applied to the screen so as to be parallel to the horizontal section of the screen is provided. I do.

With this configuration, when the green component of the image light synthesized by the color synthesizing unit is not parallel to the horizontal cross section of the screen, the polarization direction adjusting unit controls the horizontal cross section of the screen. Is adjusted to be parallel to

Preferably, the polarization directions of all the color components of the image light applied to the screen are parallel to the horizontal section of the screen.

More specifically, the color components in the polarization direction orthogonal to the vertical section of the screen in the image light combined by the color combining means are selectively adjusted to be parallel to the vertical section of the screen. It is characterized by comprising a polarization direction adjusting means.

With such a configuration, of the image light synthesized by the color synthesizing means, the color component in the polarization direction orthogonal to the horizontal section of the screen is selectively made parallel to the horizontal section of the screen. It is adjusted to become.

Further, the present invention provides a light source lamp, a color separating means for separating light emitted from the light source lamp into a plurality of color components, and a plurality of optical modulators for optically modulating each color light separated by the separating means. A liquid crystal panel, a color synthesizing means for synthesizing the respective color lights modulated by the liquid crystal panel, and a projection means for projecting the image light color-synthesized by the color synthesizing means from an oblique direction to a screen. In the rear projection display device, the polarization direction of at least the green component of the image light applied to the screen is parallel to a plane including the image light applied to the screen and the normal to the screen. It is characterized by the following.

When projecting image light obliquely onto the screen, the angle between the principal ray of light incident on the screen and the normal to the screen includes the image light applied to the screen and the normal to the screen. It is maximum in the plane. Therefore, the polarization direction of the green component of the image light, which has high relative luminous efficiency to the human eye, is parallel to the plane containing the image light irradiated to the screen and the normal line of the screen, so that the image light can be reflected on the back of the screen. The amount of light reflected and lost is reduced.

Specifically, the polarization direction of at least the green component of the image light applied to the screen is adjusted so as to be parallel to a plane including the image light applied to the screen and the normal line of the screen. It is characterized by comprising a polarization direction adjusting means.

With such a configuration, when the green component of the image light synthesized by the color synthesizing means is not parallel to a plane including the image light irradiated on the screen and the normal line of the screen, Is adjusted by the polarization direction adjusting means so as to be parallel to a plane including the image light irradiated on the screen and the normal line of the screen.

Preferably, the polarization directions of all the color components of the image light applied to the screen are parallel to the horizontal section of the screen.

Specifically, of the image light synthesized by the color synthesizing means, a color component in a polarization direction orthogonal to a plane including the image light irradiated to the screen and the screen normal is selectively converted to a plane. It is characterized in that it is provided with a polarization direction adjusting means for adjusting the parallel direction.

With such a configuration, of the image light synthesized by the color synthesizing means, a color component in a polarization direction orthogonal to a plane including the image light applied to the screen and the normal to the screen can be obtained. The adjustment is made so as to be parallel to a plane including the image light selectively irradiated on the screen and the normal line of the screen.

Specifically, the polarization direction adjusting means comprises a retardation plate.

Further, the projection means includes a plurality of aspherical mirrors that function as lenses.

The present invention also relates to a rear projection display device for irradiating image light from obliquely below or obliquely above the screen rear surface and observing an image from the screen front side. The maximum value i-max of the angle formed between the projected image light and the principal ray
And the minimum value i-min, and the angle α at which the reflectance with respect to the screen back surface is minimum in the reflectance characteristic of light having a polarization direction parallel to the vertical cross section of the screen,
It is characterized by satisfying i-min <α <i-max.

With such a configuration, light having a polarization direction parallel to the vertical cross section of the screen,
Irradiation is performed on the rear surface of the screen in a range including an angle α at which the reflectance with respect to the screen becomes the lowest with respect to the normal line of the rear surface of the screen.

The maximum value j-max and the minimum value j-min of the angle between the normal line of the screen surface and the principal ray of the image light applied to the screen surface, and the angle parallel to the vertical section of the screen. In the reflectance characteristic of light having a polarization direction, the angle β at which the reflectance with respect to the screen surface is minimum satisfies j-min <β <j-max.

With such a configuration, light having a polarization direction parallel to the vertical cross section of the screen,
Irradiation is performed on the screen surface within a range including an angle β at which the reflectance on the screen rear surface becomes the lowest with respect to the normal line of the screen back surface.

More specifically, the screen includes a Fresnel lens, and the screen surface is an inclined surface of a ring-shaped projection in the Fresnel lens.

Further, the polarization direction of at least the green component of the image light applied to the screen is parallel to the vertical section of the screen.

By making the polarization direction of the green component of the image light, which has high relative luminous efficiency to the human eye, parallel to the vertical section of the screen, the amount of light which is lost by reflecting the image light on the back surface of the screen is reduced. .

Further, according to the present invention, in a rear projection type display device in which image light is emitted obliquely to the back surface of the screen and an image is observed from the front surface side of the screen, the normal of the back surface of the screen and the back surface of the screen are irradiated. Value i-max and minimum value im of the angle formed by the principal ray of the image light
in, and the angle α at which the reflectance with respect to the screen back surface becomes minimum in the reflectance characteristic of light having a polarization direction parallel to the horizontal cross section of the screen is i-min <α <
It is characterized by satisfying i-max.

With such a configuration, light having a polarization direction parallel to the horizontal cross section of the screen,
Irradiation is performed on the rear surface of the screen within a range including an angle α at which the reflectance on the rear surface of the screen becomes the lowest with respect to the normal line of the rear surface of the screen.

The maximum value j-max and the minimum value j-min of the angle between the normal to the clean surface and the principal ray of the image light irradiated to the screen surface, and the angle parallel to the horizontal section of the screen. In the reflectance characteristic of light having a polarization direction, the angle β at which the reflectance with respect to the screen surface is minimum satisfies j-min <β <j-max.

With such a configuration, light having a polarization direction parallel to the horizontal cross section of the screen,
Irradiation is performed on the screen surface within a range including an angle β at which the reflectance on the screen rear surface becomes the lowest with respect to the normal line of the screen back surface.

Specifically, the screen includes a Fresnel lens, and the screen surface is an inclined surface of a ring-shaped projection in the Fresnel lens.

[0053] Further, the polarization direction of at least the green component of the image light applied to the screen is parallel to the horizontal section of the screen.

By making the direction of polarization of the green component of the image light, which has high relative luminous efficiency to the human eye, parallel to the horizontal section of the screen, the amount of image light reflected off the screen and lost is reduced. .

Further, according to the present invention, in a rear projection display device in which image light is obliquely applied to the back surface of a screen and an image is observed from the front surface side of the screen, the normal of the back surface of the screen and the image applied to the back surface of the screen are provided. The maximum value i-max and the minimum value i-mi of the angle between the light and the principal ray
n, and the angle α at which the reflectance with respect to the screen back surface is minimized in the reflectance characteristic of light having a polarization direction parallel to a plane including the image light irradiated on the screen back surface and the normal to the screen back surface is i −min <α <im
ax.

With such a configuration, light having a polarization direction parallel to a plane including the image light irradiated on the back surface of the screen and the normal line of the back surface of the screen is perpendicular to the normal line of the back surface of the screen. Irradiation is performed on the back surface of the screen within a range including the angle α at which the reflectance with respect to the screen becomes lowest.

Further, the maximum value j-max and the minimum value j-min of the angle formed between the normal to the screen surface and the principal ray of the image light applied to the screen surface, and the image light applied to the screen surface In the reflectance characteristic of light having a polarization direction parallel to a plane including the normal to the screen surface, the angle β at which the reflectance with respect to the screen surface is minimum satisfies j-min <β <j-max. Features.

With such a configuration, light having a polarization direction parallel to a plane including the image light irradiated on the screen surface and the normal to the screen surface can be transmitted to the normal to the screen surface. Is irradiated to the screen surface in a range including the angle β at which the reflectance on the screen surface becomes lowest.

Specifically, the screen includes a Fresnel lens, and the screen surface is an inclined surface of a ring-shaped projection in the Fresnel lens.

Further, the polarization direction of at least the green component of the image light applied to the screen is parallel to a plane including the image light applied to the back surface of the screen and the normal to the back surface of the screen. Features.

The polarization direction of the green component of the image light, which has high relative luminous efficiency to the human eye, is made parallel to the plane including the image light irradiated on the screen surface and the normal to the screen surface. Is reflected on the back surface of the screen and the amount of light lost is reduced.

[0062]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A rear projection display according to an embodiment of the present invention will be described below with reference to the drawings.
In the following description, a coordinate system is used in which the width direction of the rectangular screen 7 is the x-axis, the height direction of the screen 7 is the y-axis, and the direction perpendicular to the screen 7 is the z-axis.

In this embodiment, FIGS. 1 and 2 show a schematic configuration of a rear projection type display device. FIG. 1 is a sectional view and FIG. 2 is a front view. FIGS. 3 and 4 show a schematic configuration of a projection unit in the rear projection display device of FIG.
3 is a top view and FIG. 4 is a side view. FIG. 5 is an enlarged sectional view showing a configuration of a screen in the rear projection display device of FIG. FIG. 6 is a graph showing the reflectance characteristics of light entering the acrylic resin from the air, FIG. 7 is a graph showing the reflection characteristics of light entering the air from the acrylic resin,
FIG. 8 is a graph showing the relative luminous efficiency characteristics of a person.

As shown in FIG. 1, the rear projection type display device in this embodiment includes a projection unit 2 for generating image light,
Screen 7 on which the image light is projected to form an image
And first to fourth mirrors 3 to 6 for guiding image light emitted from the projection unit 2 to the screen 7, and a housing 1 for integrally holding these.

The first to third mirrors 3 to 5 constitute an imaging system. The first mirror 3 has an aspherical concave surface shape, the second and third mirrors 4 and 5 each have an aspherical convex surface shape, and the astigmatism of the image light depends on the shape of each mirror of the imaging system. Aberrations such as and coma are corrected, and the image is enlarged. Then, the image light emitted from the projection unit 2 is sequentially reflected by the first to third mirrors 3 to 5, and then is applied to the fourth mirror 6 arranged on the back surface of the housing 1. The image light applied to the fourth flat mirror 6 is applied obliquely from below to the back surface of the screen 7 disposed in the front opening of the housing 1 to form an image.

As shown in FIG. 3, the projection unit 2 is a so-called three-panel type. The light source 21 includes the reflector 2
1b and a metal halide lamp 21a, and the white light emitted from the light source 21 is a dichroic mirror 2
At 2 and 23, it is separated into three colors. The first dichroic mirror 22 selectively reflects red light of white light emitted from the metal halide lamp 21a and transmits light of other color components. The second dichroic mirror 23 selectively reflects green light and transmits other color components.

The white light emitted from the metal halide lamp 21a is reflected by the reflector 21a and has a UV / I
After the ultraviolet and infrared rays have been removed by an R filter (not shown), the first dichroic mirror 22
Irradiated at an angle of degrees. First dichroic mirror 2
The red light reflected by 2 is guided by the first reflection mirror 24 to the first liquid crystal panel 27r for red. The light transmitted through the first dichroic mirror 122 is applied to the second dichroic mirror 23 at an angle of 45 degrees. Of the light transmitted through the first dichroic mirror 122, the green light is the second dichroic mirror 123.
And the second liquid crystal panel 12 for green
It is led to 7 g. The remaining blue light transmitted through the second dichroic mirror 23 is transmitted to the second and third reflection mirrors 2.
The light is guided to the third liquid crystal panel 27b for blue by the light emitting elements 5 and 26. Further, the blue light transmitted through the second dichroic mirror 23 is sequentially reflected by the second and third mirrors 25 and 26, and then is irradiated on the third liquid crystal panel 27b.

The red light guided to the first liquid crystal panel 27r for red is subjected to optical modulation according to the red image information, and then enters the main surface 28r of the dichroic prism 28 for color synthesis. Is done. The green light guided to the second liquid crystal panel 27g for green light is emitted from the second liquid crystal panel 27g.
After optical modulation corresponding to green image information is performed, the main surface 28 of the dichroic prism 28 for color synthesis
g. On the other hand, the third liquid crystal panel 27 for blue
The blue light guided to b is subjected to optical modulation in accordance with blue image information by the third liquid crystal panel 27b, and then enters the main surface 28b of the dichroic prism 28 for color synthesis.

Then, of the red light incident from the main surface 28r of the dichroic prism 28, S-polarized light, that is, a component having a polarization direction perpendicular to the xz plane is reflected by the bonding surface 28x with respect to the bonding surface 28x. You. Also, of the green light incident from the main surface 28g of the dichroic prism 28, P-polarized light, that is,
A component having a polarization direction parallel to the xz plane is the bonding surface 28.
x and 28y are transmitted. Further, of the blue light incident from the main surface 28b of the dichroic prism 28,
S-polarized light with respect to y, that is, a component having a polarization direction perpendicular to the xz plane is reflected at the joint surface 28y.

As described above, each of the liquid crystal panels 27r, 27
Each color light optically modulated according to the color information of each color in g and 27b is subjected to color synthesis by the dichroic prism 28. The color-combined image light is emitted from the main surface 28c of the dichroic prism 28 and
At 9 the polarization directions are each rotated 90 degrees and the light is applied to the imaging system.

The main surface 28c of the dichroic prism 28
Of the image light emitted from the camera, red light is S-polarized light with respect to the bonding surface 28x, green light is P-polarized light with respect to the bonding surfaces 28x and 28y, and blue light is S-polarized with respect to the bonding surface 28y. Then, the polarization directions are rotated by 90 degrees by the λ / 2 retardation plate 29, and the red light is
Polarized light, green light is S-polarized with respect to the joining surfaces 28x and 28y,
The blue light becomes P-polarized light with respect to the bonding surface 28y.

The image light transmitted through the λ / 2 phase difference plate 29 is
As shown in FIG. 1, the light is sequentially reflected by first to third mirrors 3 to 5 constituting an image forming system, and then is irradiated to a fourth mirror 6 arranged on the back surface of the housing 1. Aberrations such as astigmatism and coma of image light are corrected by the shape of each mirror of these imaging systems, and an image is enlarged.

The image light applied to the fourth flat mirror 6 is applied to the back surface of the screen 7 from obliquely below. At this time, the image light applied to the back surface of the screen 7 is such that the red light is S-polarized with respect to the screen 7, that is, the polarization direction is perpendicular to the yz plane. Further, the green light becomes P-polarized light with respect to the screen 7, that is, a polarization direction parallel to the yz plane. In addition, blue light is
S-polarized light, that is, a polarization direction perpendicular to the yz plane. This yz plane corresponds to a vertical section of the screen 7.

As shown in FIG. 5, the screen 7 has a Fresnel lens screen 71 made of acrylic resin and a lenticular lens screen 72.
The image light reflected by the mirror 6 is applied to the back surface 71a of the Fresnel lens screen 71.

At this time, the Fresnel lens screen 71
The angle i formed between the normal A to the back surface 71a of the lens and the principal ray of the image light radiated therefrom is a maximum i-max at the upper end corners C1 and C2 (see FIG. 1) of the Fresnel lens screen 71, and the lower end is It becomes the minimum i-min at the central portion C3 (see FIG. 1). Here, the first to fourth mirrors 3 to 6 are designed such that i-max is 58.27 degrees and i-min is 32.27 degrees.

FIG. 6 is a graph showing the reflectance characteristics of light incident on the acrylic resin from the air. Here, the refractive index of air is 1.00, and the refractive index of acrylic resin is 1.492.
And By irradiating the screen 170 with image light obliquely, light is incident from the air at a certain incident angle on the acrylic resin.

By the way, as shown in FIG. 6, the reflectance of the light radiated to the acrylic resin constituting the Fresnel lens screen 71 from the air depends on the light radiated to the acrylic resin and the portion irradiated with the light. It changes according to the angle between the normal line of the acrylic resin and the incident angle θ1. As shown by the dashed line in the figure, the reflectance characteristic S of the light in the polarization direction perpendicular to the plane including the light irradiated to the acrylic resin and the normal line of the acrylic resin in the portion irradiated with the acrylic resin is represented by the angle θ1. Shows a tendency that the reflectance increases as the value increases. On the other hand, as shown by the solid line, the reflectance characteristic P of the light in the polarization direction parallel to the plane including the light irradiated on the acrylic resin and the normal line of the acrylic resin in the portion irradiated with the acrylic resin is represented by the angle The reflectance tends to decrease as θ1 approaches α, which takes the minimum value. The angle α at which the minimum value is obtained is an angle at which the P component of the reflected light becomes 0 and the reflected light becomes perfect plane polarized light, and the incident angle at such an angle is called a polarization angle. The polarization angle α is as shown in the following equation 1, assuming that the refractive indexes on both sides of the boundary are n1 and n2.

[0078]

Tan α = n2 / n1

More specifically, the angle α when light enters the acrylic resin from the air is approximately 56 degrees according to the above equation.

For this reason, the Fresnel lens screen 71
Screen 7 out of the image light radiated on the back surface 71a of the
The reflectance of the rear surface 71a of the Fresnel lens screen 71 of red light and blue light, which are S-polarized light, with respect to FIG.
As shown by the broken line in FIG. 5, the image light emitted to the back surface 71a of the Fresnel lens screen 71 is higher than the reflectance of light emitted in parallel with the normal A of the screen 7 and the light utilization efficiency is reduced. Among them, the reflectance of the rear surface 71a of the Fresnel lens screen 71 of the P-polarized green light with respect to the screen 7 is, as indicated by the solid line in FIG. It becomes lower than the reflectance, and the light use efficiency increases.

In general, it is known that green light greatly affects the brightness of human vision as compared with red light and blue light. In other words, the human eye feels light having a wavelength of 555 nm corresponding to green to be the brightest (high visibility). Wavelength 555 corresponding to green
FIG. 8 shows the luminosity factor in each wavelength range based on the luminosity factor for nm. According to the figure, assuming that the visibility for green is 1, the visibility at a wavelength of 630 nm corresponding to red is approximately 0.265, and the visibility at a wavelength of 470 nm corresponding to blue is approximately 0.091.

As described above, when irradiating the screen 7 with the image light obliquely, since the visibility of the green light is much higher than the red light and the blue light, the red light and the blue light are applied to the screen 7. By increasing the green light to the P-polarized light with respect to the screen 7, the luminance that rises can be made larger than the luminance that decreases by making the S-polarized light, and overall high luminance can be achieved. . Further, with the increase in brightness, the Fresnel lens screen 7
The amount of light reflected by the back surface 71a of the first lens unit decreases, so that a double image due to reflection of the reflected light can be reduced, and the image quality can be improved. Preferably, all the color components need only be P-polarized light with respect to the screen 7.

Further, since the angle i between the principal ray of the image light applied to the screen 7 and the normal A of the screen 7 is set so as to satisfy the following equation 2, the use of the light of the P-polarized light component itself is used. Efficiency can be improved, and higher luminance can be achieved.

[0084]

## EQU2 ## i-min <α <i-max

Next, the image light transmitted through the back surface 71a of the Fresnel lens screen 71 is refracted on the back surface 71a at an angle k1 according to Snell's law, and then formed in a ring shape on the emission side of the Fresnel lens screen 71. Irradiation is performed on the inclined surface 71b of the projected protrusion.

At this time, the Fresnel lens screen 71
The angle j between the normal line B to the inclined surface 71b and the principal ray of the image light applied to the inclined surface 71b is at most j-m on the inclined surface 71b of each projection of the Fresnel lens screen 71.
ax, the inclined surface 71b so as to have an angle of the minimum j-min.
Angle is set. Here, j-max is 3
8.36 degrees, j-min is 22.57 degrees,
The inclination angle τ of each inclined surface 71b is set.

By the way, as shown in FIG. 7, the reflectance of the light emitted from the acrylic resin forming the Fresnel lens 71 into the air depends on the light traveling in the acrylic resin and the acrylic resin in the portion where the light is emitted. Changes in accordance with the angle θ2 formed with the normal line. As shown by the dashed line in the figure, the reflectance characteristic S ′ of the light in the polarization direction perpendicular to the plane including the light traveling in the acrylic resin and the normal line of the acrylic resin in the portion where the light is emitted is represented by the angle θ2. Shows a tendency that the reflectance increases as the value increases. On the other hand, as shown by a solid line in the figure, the reflectance characteristic P ′ of light in a polarization direction parallel to a plane including the light traveling in the acrylic resin and the normal line of the acrylic resin at the portion where the light is emitted is shown. Is
The reflectivity tends to decrease as the angle θ2 approaches the polarization angle β having a minimum value. Specifically, when light is emitted from the acrylic resin to the air, the angle β is approximately 34 degrees from Equation (1).

For this reason, the Fresnel lens screen 71
In the image light applied to the inclined surface 71b of the ring-shaped projection on the emission side of the light, the reflectance of the inclined surface 71b of red light and blue light, which are S-polarized light, with respect to the screen 7 is
As shown by a broken line S ′ in FIG.
The slope of green light that is P-polarized light with respect to the screen 7 of the image light emitted to the inclined surface 71b, although the reflectance becomes higher than the reflectance of the light emitted in parallel with the light and the light use efficiency decreases. The reflectance at 71b is indicated by a solid line P in FIG.
As shown by ', the reflectance becomes lower than the reflectance of light emitted in parallel with the normal B of the inclined surface 71b, and the light use efficiency increases.

Therefore, similarly to the case where the rear surface 71a of the Fresnel lens screen 71 is irradiated with the image light from the air, the red light and the blue light are applied to the screen 7 by the S.
By increasing the green light to the P-polarized light with respect to the screen 7, the luminance that can be increased can be made larger than the luminance that is decreased by the polarized light, so that the overall luminance can be increased. Further, since the reflected light on the inclined surface 71b of the Fresnel lens screen 71 is reduced, a double image caused by the reflected light can be reduced, and the image quality can be improved. Preferably,
All color components need only be P-polarized light.

Also, since the angle j between the principal ray of the image light applied to the inclined surface 71b of the screen 7 and the normal B of the inclined surface 71b is set so as to satisfy the following equation (3),
The light use efficiency of the P-polarized light component itself can be improved, and further higher luminance can be achieved.

[0091]

## EQU3 ## j-min <β <j-max

Then, the image light transmitted through the inclined surface 71b of the Fresnel lens screen 7 is refracted at the inclined surface 71b at an angle k2 according to Snell's law, and then radiated to the lenticular lens screen 72, and by its diffusing action. An image is formed.

[0093] In the present embodiment, the case where the image light is irradiated from obliquely below the screen 7 has been described. However, the image light may be irradiated from the oblique side of the screen 7. In this case, the green light may be adjusted so as to be P-polarized light with respect to the screen 7, that is, a polarization direction parallel to the xz plane.

In this embodiment, the case where the polarization direction of the green light is adjusted so as to be parallel to the yz plane has been described. However, it is preferable that the principal ray of the image light and the image light be adjusted. It is better to make adjustments so as to be parallel to a plane including the normal line in the portion where is irradiated.

In this embodiment, the polarization direction of the green light is changed by the λ / 2 retardation plate 29 to the screen 7.
Was adjusted to be S-polarized light to P-polarized light, but a narrow-band retarder that selectively adjusts the polarization direction of green light so that the screen 7 changes from S-polarized light to P-polarized light may be used. Good. In this case, since the polarization directions of the red light and the blue light do not change, all the image light
It is possible to adjust so as to be polarized light.

Further, in this embodiment, the image forming system is constituted by the first to third mirrors 3 to 5, but it is needless to say that the same effect can be obtained by using a lens system.

[0097]

According to the present invention, when the screen is irradiated with image light obliquely, at least the green component is converted to P-polarized light with respect to the screen, whereby reflection on the screen can be reduced. Not only can the brightness be increased, but also a double image due to reflection of reflected light on the screen can be reduced, and image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a rear projection display device according to an embodiment of the present invention.

FIG. 2 is a front view of the same.

FIG. 3 is a top view illustrating a schematic configuration of a projection unit in the rear projection display device of FIG.

FIG. 4 is a side view of the same.

FIG. 5 is a partially enlarged cross-sectional view showing a schematic configuration of a screen in the rear projection display device of FIG. 1;

FIG. 6 is a graph showing reflectance characteristics of light incident on the acrylic resin from the air.

FIG. 7 is a graph showing a reflection characteristic of light emitted from an acrylic resin into the air.

FIG. 8 is a graph showing human luminous efficiency characteristics.

FIG. 9 is a cross-sectional view illustrating a schematic configuration of a conventional rear projection display device.

FIG. 10 is a top view illustrating a schematic configuration of a projection unit in the rear projection display device of FIG. 9;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 housing 2 projection unit 29 λ / 2 retardation plate 3 first reflection mirror 4 second reflection mirror 5 third reflection mirror 6 fourth reflection mirror 7 screen 71 Fresnel lens screen 72 lenticular lens screen

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03B 33/12 G09F 9/00 360N G09F 9/00 360 H04N 9/31 Z H04N 9/31 G02F 1/1335 530

Claims (29)

[Claims] 1. A light source lamp, a color separating means for separating light emitted from the light source lamp into a plurality of color components, and a plurality of liquid crystal panels for optically modulating each color light separated by the color separating means. A color synthesizing means for synthesizing each color light modulated by the liquid crystal panel, and a projection means for projecting the image light color-synthesized by the color synthesizing means onto the screen from obliquely above or below. A rear projection display device, comprising: a polarization direction of at least one color component of image light emitted to the screen is parallel to a vertical cross section of the screen. 2. The rear projection display device according to claim 1, wherein the at least one color component is a green component. 3. A polarization direction adjusting means for adjusting a polarization direction of at least a green component of the image light synthesized by the color synthesizing means so as to be parallel to a vertical section of the screen. 3. The rear projection display device according to claim 2, wherein: 4. The screen according to claim 1, wherein the polarization directions of all the color components of the image light applied to the screen are parallel to a vertical section of the screen.
2. The rear projection display device according to 1. 5. A color component in a polarization direction orthogonal to a vertical section of the screen in the image light combined by the color combining means is selectively adjusted to be parallel to the vertical section of the screen. 5. The rear projection display device according to claim 4, further comprising a polarization direction adjusting means. 6. A maximum value i-max and a minimum value i-min of an angle between a normal line of the screen back surface and a principal ray of image light applied to the screen back surface, and a vertical section of the screen. 2. The rear projection according to claim 1, wherein the angle α at which the reflectance with respect to the screen back surface is minimum in the reflectance characteristics of light having parallel polarization directions satisfies i-min <α <i-max. 3. Type display device. 7. A maximum value j-max and a minimum value j-min of an angle between a normal line of the screen surface and a principal ray of image light applied to the screen surface, and a vertical section of the screen. 2. The rear projection according to claim 1, wherein an angle β at which the reflectance of the light having a parallel polarization direction with respect to the screen surface becomes minimum satisfies j-min <β <j-max. 3. Type display device. 8. The rear projection display device according to claim 7, wherein the screen includes a Fresnel lens, and the screen surface is an inclined surface of a ring-shaped protrusion in the Fresnel lens. 9. The rear projection type according to claim 6, wherein the polarization direction of at least the green component of the image light applied to the screen is parallel to a vertical section of the screen. Display device. 10. A light source lamp, color separation means for separating light emitted from the light source lamp into a plurality of color components, and a plurality of liquid crystal panels for optically modulating each color light separated by the color separation means. And a color synthesizing means for synthesizing each color light modulated by the liquid crystal panel, and a projection means for projecting the image light color-synthesized by the synthesizing means from an oblique side to the screen. At least one of the image light radiated to
A rear projection display device, wherein the polarization directions of the two color components are parallel to a horizontal cross section of the screen. 11. The rear projection display device according to claim 10, wherein the at least one color component is a green component. 12. A polarization direction adjusting means for adjusting a polarization direction of at least a green component of image light applied to the screen so as to be parallel to a horizontal section of the screen. A rear projection display device according to claim 11. 13. The rear projection according to claim 10, wherein the polarization directions of all color components of the image light applied to the screen are parallel to a horizontal section of the screen. Type display device. 14. A color component in a polarization direction orthogonal to the vertical section of the screen in the image light combined by the color combining means is selectively adjusted to be parallel to the vertical section of the screen. 14. The rear projection display device according to claim 13, further comprising a polarization direction adjusting unit. 15. A maximum value i-max and a minimum value i-min of an angle formed between a normal line of the screen back surface and a principal ray of image light applied to the screen back surface, and a horizontal cross section of the screen. In the reflectance characteristic of light having a parallel polarization direction, the angle α at which the reflectance with respect to the screen back surface becomes minimum is i-min <α <i-max.
The rear projection display device according to claim 10, wherein the following condition is satisfied. 16. A maximum value j-max and a minimum value j-min of an angle formed between a normal line of the screen surface and a principal ray of image light emitted to the screen surface, and a horizontal section of the screen. The angle β at which the reflectance with respect to the screen surface becomes minimum in the reflectance characteristic of light having a parallel polarization direction is j-min <β <j-max.
The rear projection display device according to claim 10, wherein the following condition is satisfied. 17. The screen according to claim 16, wherein the screen includes a Fresnel lens, and the screen surface is an inclined surface of a ring-shaped protrusion in the Fresnel lens.
2. The rear projection display device according to 1. 18. The rear projection type according to claim 15, wherein a polarization direction of at least a green component of the image light applied to the screen is parallel to a horizontal cross section of the screen. Display device. 19. A light source lamp, color separation means for separating light emitted from the light source lamp into a plurality of color components, and a plurality of liquid crystal panels for optically modulating each color light separated by the color separation means. And a color synthesizing means for synthesizing each color light modulated by these liquid crystal panels, and a projection means for projecting the image light color-synthesized by the color synthesizing means to the screen from an oblique direction, At least one of the video light illuminated on the screen
A rear projection display device, wherein the polarization directions of the two color components are parallel to a plane including the image light irradiated on the screen and a normal line of the screen. 20. The rear projection display according to claim 19, wherein the at least one color component is a green component. 21. A polarization direction of at least a green component of the image light applied to the screen is adjusted to be parallel to a plane including the image light applied to the screen and a normal to the screen. 21. The rear projection type display device according to claim 20, further comprising a polarization direction adjusting unit. 22. The rear projection according to claim 19, wherein polarization directions of all color components of the image light irradiated on the screen are parallel to a horizontal section of the screen. Type display device. 23. A color component in a polarization direction orthogonal to a plane including the image light applied to the screen and a normal line of the screen, out of the image light synthesized by the color synthesizing means, selectively on the plane. 23. The rear-projection display device according to claim 22, further comprising a polarization direction adjusting unit that adjusts the polarization direction so as to be parallel to the display. 24. A maximum value i-max and a minimum value i-min of an angle formed between a normal line of the screen back surface and a principal ray of image light applied to the screen back surface, and an image applied to the screen back surface. In the reflectance characteristic of light having a polarization direction parallel to a plane including light and the normal to the screen back surface, the angle α at which the reflectance with respect to the screen back surface is minimized is i-min <α <i-max.
The rear projection display device according to claim 19, wherein the following condition is satisfied. 25. A maximum value j-max and a minimum value j-min of an angle formed between a normal to the screen surface and a principal ray of image light applied to the screen surface, and an image applied to the screen surface. In the reflectance characteristic of light having a polarization direction parallel to a plane including light and the normal to the screen surface, the angle β at which the reflectance with respect to the screen surface is minimum is j-min <β <j-max.
The rear projection display device according to claim 19, wherein the following condition is satisfied. 26. The screen according to claim 19, wherein the screen includes a Fresnel lens, and the screen surface is an inclined surface of a ring-shaped protrusion in the Fresnel lens.
2. The rear projection display device according to 1. 27. A polarization direction of at least a green component of the image light applied to the screen is parallel to a plane including the image light applied to the screen back surface and a normal to the screen back surface. 20. The rear projection display device according to claim 19, wherein: 28. The apparatus according to claim 3, wherein said polarization direction adjusting means comprises a retardation plate.
4. The rear projection display device according to any one of 3. 29. The apparatus according to claim 1, wherein said projection means includes a plurality of aspherical mirrors that function as lenses.
20. The rear projection display device according to any one of claims 10 and 19.